The present invention relates to a quench detector for detecting changes in the conductivity of a superconducting coil and for monitoring the integrity of the leads connected to the coil to determine whether they have become open or short circuited.
In superconducting magnets, local increases in the magnetic field or movement of the conductor produces normally conducting, or resistive, regions in the coil. Due to the heating associated therewith, these undesired, normally conducting, resistive regions may rapidly spread throughout the entire magnet. After such a transition, the energy supply must be interrupted as quickly as possible and the current reduced to zero to prevent the entire magnet from being damaged or destroyed as a result of its being driven into the normal state. The reliable operation of a superconducting magnet therefore requires the early detection of a transition to normal conduction.
Quench detectors are known in which the superconducting coil is divided by a center tap into two coil elements which form part of a bridge circuit for monitoring the coil. A disadvantage of these known devices is that a break in one or more of the measuring leads connected to the superconducting coil being monitored cannot be detected. Consequently, a transition to normal conduction in one partial region of the superconducting coil will not be detected early enough to prevent with sufficient certainty the destruction of the coil.
It is an object of the present invention to provide a quench detector having a reliability which is substantially increased over those of the prior art thereby also improving the operating reliability of the superconducting coil being monitored.